Indoor Air Quality and Health: A Practical Guide

Why Indoor Air Quality Matters

Most people spend the majority of their time indoors — the Environmental Protection Agency (EPA) estimates that the average person spends approximately 90% of their time in indoor environments. Yet indoor air can be significantly more polluted than outdoor air, sometimes by a factor of 2 to 5 times, according to the EPA.

In Ireland, where the climate encourages people to stay indoors for much of the year, indoor air quality is a particularly relevant health consideration. The HSE recognises that poor indoor air quality can contribute to respiratory problems, allergic reactions, headaches, fatigue, and irritation of the eyes, nose, and throat.

The WHO estimates that 3.2 million premature deaths globally each year are attributable to indoor air pollution, primarily from household use of solid fuels for cooking and heating. While this figure is driven largely by developing countries, indoor air quality in Irish homes can be compromised by a range of factors including poor ventilation, damp and mould, combustion sources, and chemical emissions from household products.

Common Indoor Air Pollutants

Understanding the sources of indoor air pollution is the first step toward improving air quality in your home:

Particulate matter (PM2.5 and PM10) consists of tiny particles that can penetrate deep into the lungs. Sources include solid fuel fires (turf, coal, wood), cooking, candles, and tobacco smoke. Ireland’s traditional use of solid fuels for home heating means that particulate matter is a relevant concern, particularly in older homes and rural areas.

Volatile organic compounds (VOCs) are gases emitted from a wide range of products including paints, cleaning agents, air fresheners, personal care products, and new furniture or carpets. Some VOCs, such as formaldehyde and benzene, are classified as carcinogenic. Concentrations of VOCs tend to be higher indoors than outdoors.

Carbon monoxide (CO) is a colourless, odourless gas produced by the incomplete combustion of fossil fuels. Sources include gas boilers, fires, and stoves. Carbon monoxide can be lethal at high concentrations, and the HSE strongly recommends installing carbon monoxide alarms in all homes with combustion appliances.

Mould and damp are common problems in Irish homes due to the climate. Mould releases spores and mycotoxins into the air, which can trigger respiratory symptoms, allergic reactions, and asthma exacerbations. The HSE advises addressing damp and mould promptly, as prolonged exposure may be associated with respiratory health problems.

Radon is a naturally occurring radioactive gas that seeps into buildings from the ground. Ireland has areas of elevated radon, and the EPA identifies radon as the leading environmental cause of lung cancer after smoking. The EPA provides free radon risk maps and recommends testing in all Irish homes, particularly in high-radon areas.

Practical Steps to Improve Indoor Air Quality

Ventilation

Adequate ventilation is the most important factor in maintaining good indoor air quality. Opening windows for even 10-15 minutes several times per day allows fresh air to circulate and reduces the concentration of indoor pollutants. This is particularly important during and after activities that generate pollutants, such as cooking, cleaning, or using a fire.

In newer homes with mechanical ventilation systems, ensure these are properly maintained and filters are changed according to manufacturer guidelines. Extractor fans in kitchens and bathrooms should be used during cooking and bathing and left running for 15-20 minutes afterwards.

Reduce Pollutant Sources

Avoid smoking indoors. Tobacco smoke contains over 7,000 chemicals, many of which are carcinogenic. The HSE identifies secondhand smoke as a significant indoor pollutant with established health risks.
Choose low-VOC products when painting, renovating, or purchasing new furniture. Many paints and cleaning products now offer low-VOC alternatives.
Use extractor hoods when cooking to remove combustion products and cooking fumes. Gas hobs produce nitrogen dioxide and particulate matter during use.
Service combustion appliances annually. Gas boilers, stoves, and fireplaces should be professionally serviced to ensure they are operating safely and efficiently.
Minimise use of scented candles and air fresheners, which can release VOCs and particulate matter.

Address Damp and Mould

The HSE recommends addressing the root cause of damp rather than simply cleaning visible mould. Common causes include condensation (inadequate ventilation), rising damp, and leaks. Improving ventilation, using dehumidifiers in problem areas, drying clothes outdoors or in well-ventilated spaces, and repairing structural issues are all important steps.

If mould covers an area larger than approximately one square metre, the HSE advises seeking professional help for removal.

Test for Radon

The EPA provides a free radon risk map at radon.ie to help you assess whether your home is in a high-radon area. Radon test kits are available through the EPA and take approximately three months to provide an accurate reading. If levels are above the national reference level (200 Bq/m3), remediation measures can significantly reduce radon concentrations — typically by improving underfloor ventilation or installing a radon sump.

Air Purification as a Complementary Measure

While ventilation and source control should be the primary strategies for improving indoor air quality, air purifiers with HEPA filters can serve as a useful complementary measure. HEPA filters capture 99.97% of airborne particles as small as 0.3 microns, including dust, pollen, mould spores, and pet dander.

Air purifiers may be particularly beneficial for people with respiratory conditions, allergies, or compromised immune systems. They do not replace adequate ventilation but can help reduce particulate matter concentrations in specific rooms.

For those interested in exploring air purification options, our air purifier guide and HEPA air purifier recommendations provide practical information to help you choose an appropriate model.

Maintaining good indoor air quality complements other health-promoting habits, including good nutrition and adequate sleep, as part of an overall approach to wellbeing.

Key Takeaways

Indoor air can be 2-5 times more polluted than outdoor air, and most people spend approximately 90% of their time indoors
Common indoor pollutants include particulate matter from solid fuels, VOCs from household products, carbon monoxide, mould, and radon
Regular ventilation — opening windows for 10-15 minutes several times daily — is the most effective way to improve indoor air quality
All Irish homes should be tested for radon, particularly in EPA-identified high-risk areas
Carbon monoxide alarms are strongly recommended by the HSE for all homes with combustion appliances

Frequently Asked Questions

How do I know if my indoor air quality is poor?

Common signs of poor indoor air quality include persistent stuffiness, condensation on windows, musty or chemical odours, and occupants experiencing symptoms such as headaches, fatigue, eye irritation, or worsening respiratory conditions that improve when away from the building. Home air quality monitors are available that measure particulate matter and VOC levels, though they are not a substitute for professional assessment of specific concerns like radon.

Is radon a concern everywhere in Ireland?

Radon levels vary significantly across Ireland depending on the underlying geology. While certain areas — particularly parts of counties Galway, Clare, Mayo, Kerry, and Wicklow — have higher average radon levels, elevated radon can be found in any part of the country. The EPA recommends that all Irish homes be tested, regardless of location. Testing is straightforward and inexpensive through the EPA’s radon testing service.

Do houseplants improve indoor air quality?

While a well-known NASA study from the 1980s showed that certain houseplants can remove some VOCs from air in sealed laboratory conditions, subsequent research has concluded that the number of plants required to meaningfully improve air quality in a typical home would be impractical — potentially hundreds of plants per room. Houseplants offer other benefits (aesthetics, wellbeing), but they should not be relied upon as an air purification strategy.